You are welcome. I'm glad the workaround was successful.
I also experience this problem sometimes. Unfortunately it seems to only occur intermittently and under specific conditions, which makes it difficult to investigate. For example, I experience it when I use the IDE with my ridiculous 32 GB collection of 90 different boards platforms installed, but when I switch to a more realistic environment with only a dozen platforms then I can no longer reproduce the fault.
And when I enable the debug logging that would give me some idea of what is happening, I can no longer reproduce the fault.
And when I run the same commands with Arduino CLI directly (which is the tool that actually performs the library updates for Arduino IDE under the hood), I can no longer reproduce the fault.
A very difficult to pin down bug! I have made multiple attempts at investigating it, but previously I didn't take it very seriously because we had never received any reports from users who were affected. But there was another report of this only recently (IDE & Library update in the same time), so maybe something has changed that makes it more likely to occur?
I find that when I update each of the libraries separately using the procedure I described in my previous reply, instead of all in one go as occurs when you click the "UPDATE ALL" button in the notification, I never encounter the update process hang. So I think that we at least have a reliable workaround for the bug.